Port Otago is looking to compete with the Port of Tauranga's dredging efforts so it can attract the "superships" being used by global shipping companies.

The company said Otago was already the deepest container port in the country at 14 metres and it was looking to add a metre to attract ships of 6500 to 8000 TEU (twenty-foot equivalent unit) containers.

Tauranga and Otago are the only two ports in the country that have consent to dredge to that depth.

No formal announcement has been made on when Port Otago will begin dredging, but it has its own dredge and can carry the work out at will.

The move follows Port of Tauranga's recent announcement of a partnership with shipping company Maersk and logistics company Kotahi that would also push freight through PrimePort in Timaru.

The Timaru port is a rival of Port Otago and the Lyttelton Port Company.

Two weeks ago, the Christchurch City Council's holding company entered an agreement to buy Port Otago's 15.48 per cent stake in the Lyttelton port.

The council ultimately wants to take full ownership of the Lyttelton port and delist it from the stock exchange.